My favourite patch is my drum sequencer. Lots of blood sweat and tears were paid to get it, but I don't think that's what you mean; you mean "favourite patch available online", yeah?
Welp, then I'd have to say...granular. Specifically Robert Henke's "GrainFreeze" (well, my own osc-modded version).
Either that, or BEAP. All of it.
Or grainstretch~.
If we're counting abstractions, then M4L.vdelay~ - all the way, it's so useful, it's not even funny.
If we're counting vanilla max, then zl.maxhelp :)